Hot melt adhesive compositions

ABSTRACT

This invention relates to hot melt adhesive compositions which includes a neutralized sulfonated elastomeric polymer having about 5 to about 50 meq. of neutralized sulfonate groups per 100 grams of the neutralized sulfonated elastomeric polymer, and about 25 to about 250 parts by weight of a hydrocarbon resin of a petroleum or coal tar distillate, aliphatic dienes and mono and diolefins, cyclic olefins of 5 or 6 carbon atoms and hydrogenated poly cyclics per 100 parts by weight of the neutralized sulfonated EPDM terpolymer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to hot melt adhesive compositions which includesa neutralized sulfonated elastomeric polymer wherein the neutralizedsulfonated elastomeric polymer has about 5 to about 50 meq. ofneutralized sulfonate groups per 100 grams of the neutralized sulfonatedelastomeric polymer, and about 25 to about 250 parts by weight of ahydrocarbon resin of a petroleum or coal tar distillate, having about 5to about 6 carbon atoms the hydrocarbon resin being composed ofaliphatic dienes and monoolefins per 100 parts by weight of theneutralized sulfonated EPDM terpolymer.

Broadly speaking, synthetic adhesives used in packaging can beclassified into four categories: water based, solvent based, reactiveand hot melt adhesives. Of these four, currently the water based areused most extensively. Usually the water based adhesives are based onemulsion polymers and are applied to porous cellulosic substrates.Energy from the outside in some fashion is applied to the system toevaporate the water in order that a strong bond may be formed. Besidethis energy requirement for the formation of the bond, there is anothercomplication with the use of water based adhesive. For a uniform coatinga good uniform wetting of the substrate surface is desired, which is noteasily achieved.

With the solvent-based adhesives usually a good wetting is achieved;however, their use has been becoming extremely restrictive due toexpensive energy requirements for the evaporation of organic solventsfire hazards associated with the use of these organic solvents andemissions problems with said solvents. The strict governmentenvironmental regulations and restrictions concerning worker's exposureto solvent vapors, etc. has placed extra pressure on the packager to usenon-solvent based adhesives.

Recently the use of hot melt adhesives has been growing very rapidly inthe packaging industry. The hot melt adhesives are generally applied (asthe name implies) by conventional extrusion or coating techniques in thetemperature range of 250° to 450° F. on one of the surfaces to bebonded. The other surface is brought in contact with the hot surface fora sufficient period of time for the melt to cool, whereuponsolidification a strong and durable bond is formed.

The key requirements of resins suitable for hot melt adhesiveapplications are that they should have good physical properties, e.g.,tensile strength, etc., at ambient conditions, and they can flow easilyat fabrication temperatures. The ethylene vinyl acetate (EVA) copolymersand styrene block copolymers, such as Kraton, have been extensively usedas hot melt adhesives; however, their use has been limited largely topressure sensitive adhesives.

There is a significant demand in the marketplace today for polymersystems which exhibit good green strength or tensile properties atambient temperatures which, when heated to a predetermined temperature,will give good flow such that they may be applied to a coating orsubstrate by melt extrusion or other suitable techniques. In the past ithas been common to employ organic solutions as a way of applying acoating of a polymer system which is designed to have good adhesiveproperties. This practice is now under considerable pressure, due to thefact that the organic solvents must be evaporated from the coatinggiving rise to pollution problems and excess energy requirements.

2. Prior Art

Several U.S. Patents have described sulfonated polymers such assulfonated butyl and sulfonated EPDM in adhesive applications (e.g. U.S.Pat. No. 3,867,247 and U.S. Pat. No. 3,801,531). It is important todistinguish the instant invention over those prior art systems. Theformer patent is directed at a sulfonated butyl cement which is solventbased and is employed to laminate various substrates. It is important tonote that the instant invention differs dramatically from that patent asfollows:

(a) The adhesives of the instant invention are not deposited fromsolvents but are hot melt and require no solvents in their preferredmethod of utilization.

(b) The instant invention may optionally include a preferentialplasticizer capable of associating with the metal sulfonate groups andthereby reducing the melt viscosity of the resulting blends to make thesystems more processable.

(c) The instant invention is directed at sulfonated ethylene propyleneterpolymers or sulfonated EPDM, whereas most of the prior art deals withsulfonated butyl rubber (e.g. U.S. Pat. No. 3,867,247).

With regard to the latter point, historically EPDM systems do notpossess good tack properties and substantial art exists directed towardsimproving the adhesive characteristics of such systems. This problembecomes even more acute when EPDM is sulfonated to levels of 5 to 50milliequivalents (meq.) per 100 grams of polymer and neutralized. Theresulting compositions have been widely used as the basis forthermoplastic elastomers (i.e. U.S. Pat. Nos. 4,157,992; 4,014,831etc.). The use of these materials in such applications is, in part, ademonstration that the properties of such materials are just theopposite of those desired for adhesive. In fact such materials areremarkably devoid of tack or adhesion. The task, therefore, ofconverting such physically crosslinked materials into suitable adhesivecandidates is a particularly challenging one for two reasons: (a) theEPDM backbone is particularly unsuited for that purpose being a very dryelastomer; (b) the strong associations attributable to metal sulfonatecrosslinks further inhibit adhesion to any particular substrate.

Despite these handicaps there are some very good reasons for solving theproblems associated with converting sulfonated EPDM into a good hot meltadhesive composition. The excellent thermal stability inherent in theEPDM backbone is a very desirable property for adhesives which will beexposed to high temperatures for long times. Most adhesives based onother elastomeric backbones can suffer degradation under thoseconditions.

SUMMARY OF THE INVENTION

This invention relates to hot melt adhesive compositions which includesa neutralized sulfonated elastomeric polymer, wherein the neutralizedsulfonated elastomeric polymer is preferably an EPDM terpolymer havingabout 5 to about 50 meg. of neutralized sulfonate groups per 100 gramsof the neutralized sulfonated elastomeric polymer and about 25 to about250 parts by weight of a hydrocarbon resin of a petroleum or coal tardistillate, having about 5 to about 6 carbon atoms, said hydrocarbonresin having aliphatic dienes and monoolefins therein per 100 parts byweight of the highly unsaturated hydrocarbon rubber and optionally,about 1 to about 50 parts of a preferential plasticizer per 100 parts ofthe neutralized sulfonated polymer can be added to the composition.

GENERAL DESCRIPTION

The present invention relates to unique and novel hot melt adhesivecompositions which comprise a blend of a neutralized sulfonatedelastomeric polymer which is preferably an EPDM terpolymer, and ahydrocarbon resin, wherein to the compositions can be optionally addedan ionic preferential plasticizer oil, and/or a filler thereby modifyingthe rheological and physical properties of the hot melt adhesivecompositions.

A. Sulfonated Polymer and Process for Forming

The neutralized sulfonated elastomeric polymers of this present instantinvention are derived from unsaturated polymers wherein an EPDMterpolymer is preferred.

EPR or EPDM polymers are known in the rubber industry as very dryrubbers meaning that they are relatively non-tacky, and indeed are verylimited in adhesive applications for that reason. Therefore, the instantinvention is specifically attractive for sulfonated EPDM systems in thatthese materials possess a very high degree of ionic crosslinking whichcan be controlled by plasticization yet can be modified with the blendstaught herein to have good adhesive qualities. This combination of goodadhesion and adequate tensile properties is highly sought in a number ofadhesive applications, yet is particularly difficult to achieve with thesulfonated ethylene propylene terpolymers. This invention will describehow such elastomers can be blended to achieve some of these desirableproperties.

The EPDM terpolymers are low unsaturation polymers having about 1 toabout 10.0 wt. % olefinic unsaturation, more preferably about 2 to about8, most preferably about 3 to 7 defined according to the definition asfound in ASTM D-1418-64 and is intended to mean terpolymers containingethylene and propylene in the backbone and a diene in the side chain.Illustrative methods for producing these terpolymers are found in U.S.Pat. No. 3,280,082, British Pat. No. 1,030,289 and French Pat. No.1,386,600, which are incorporated herein by reference. The preferredpolymers contain about 40 to about 50 wt. % ethylene and about 1 toabout 10 wt. % of a diene monomer, the balance of the polymer beingpropylene. Preferably, the polymer contains about 45 to about 65 wt. %ethylene, more preferably 45 to 60 wt. % e.g., 50 wt. % and about 2.6 toabout 8.0 wt. % diene monomer, e.g., 5.0 wt. %. Such EPDM polymers aresubstantially noncrystalline meaning they possess less than 20%crystallinity as determined by X-ray techniques. The diene monomer ispreferably a non-conjugated diene. Illustrative of these non-conjugateddiene monomers which may be used in the terpolymer (EPDM) are1,4-hexadiene, dicyclopentadiene, 5-ethylidene 2-norbornene,5-methylene-2-norbornene, 5-propenyl-2-norbornene, and methyltetrahydroindene. A typical EPDM is Vistalon 2504 (Exxon Chemical Co.),a terpolymer having a Mooney viscosity (ML, 1+8, 212° F.) of about 40and having an ethylene content of about 50 wt. % and a5-ethylidene-2-norbornene content of about 5.0 wt. %. The Mn as measuredby GPC of Vistalon 2504 is about 47,000, the Mv as measured by GPC isabout 145,000 and the Mw as measured by GPC is about 174,000. AnotherEPDM terpolymer Vistalon 2504-20 is derived from Vistalon 2504 (ExxonChemical Co.) by a controlled extrusion process, wherein the resultantMooney viscosity (ML, 1+8, 212° F.) is about 20. The Mn as measured byGPC of Vistalon 2504-20 is about 26,000, the Mv as measured by GPC isabout 90,000 and the Mw as measured by GPC is about 125,000. Nordel 1320(DuPont) is another terpolymer having a Mooney viscosity (ML, 1±8, 212°F.) of about 25 and having about 53 wt. % of ethylene, about 3.5 wt. %of 1,4-hexadiene, and about 43.5 wt. % of propylene.

Another EPDM terpolymer Vistalon (MD-76-5) is a terpolymer having aMooney viscosity (ML, 1+8, 212° F.) of about 20, and Mn as measured byGPC of about 60,000 and a wt. % ethylene content of about 55.

The EPDM terpolymers of this invention have a number average molecularweight (Mn) as measured by GPC of about 10,000 to about 200,000, morepreferably of about 15,000 to about 100,000, and most preferably ofabout 20,000 to about 60,000. The Mooney viscosity (ML, 1+8, 212° F.) ofthe EPDM terpolymer is about 5 to about 60, more preferably about 10 toabout 50, most preferably about 5 to about 40. The Mv as measured by GPCof the EPDM terpolymer is preferably below about 350,000 and morepreferably below about 300,000. The Mw as measured by GPC of the EPDMterpolymer is preferably below about 500,000 and more preferably belowabout 350,000.

The sulfonated EPDM terpolymers are formed by dissolving the elastomericpolymer in a non-reactive solvent such as chlorinated aliphatic solvent,chlorinated aromatic hydrocarbon, an aromatic hydrocarbon, or analiphatic hydrocarbon such as carbon tetrachloride, dichloroethane,chlorobenzene, benzene, toluene, xylene, cyclohexane, pentane,isopentane, hexane, isohexane or heptane. The preferred solvents are thelower boiling aliphatic hydrocarbons. A sulfonating agent is added tothe solution of the elastomeric polymer and non-reactive solvent at atemperature of about -100° C. to about 100° C. for a period of time ofabout 1 to about 60 minutes, most preferably at room temperature forabout 5 to about 45 minutes; and most preferably about 15 to about 30.Typical sulfonating agents are described in U.S. Pat. Nos. 3,642,728 and3,836,511, incorporated herein by reference. The sulfonating agents areselected from an acyl sulfate, a mixture of sulfuric acid and an acidanhydride or a complex of a sulfur trioxide donor and a Lewis basecontaining oxygen, sulfur, or phosphorous. Typical sulfur trioxidedonors are SO₃, chlorosulfonic acid, fluorosulfonic acid, sulfuric acid,oleum, etc. Typical Lewis bases are: dioxane, tetrahydrofuran,tetrahydrothiophene or triethyl phosphate. The most preferredsulfonation agent for this invention is an acyl sulfate selected fromthe group consisting essentially of benzoyl, acetyl, propionyl orbutyryl sulfate. The acyl sulfate can be formed in situ in the reactionmedium or pregenerated before its addition to the reaction medium in achlorinated aliphatic or aromatic hydrocarbon.

It should be pointed out that neither the sulfonating agent nor themanner of sulfonation is critical, provided that the sulfonating methoddoes not degrade the EPDM terpolymer backbone. The reaction is quenchedwith an aliphatic alcohol such as methanol, ethanol or isopropanol, withan aromatic hydroxyl compound, such as phenol, as cycloaliphatic alcoholsuch as cyclohexanol or with water. The sulfonated EPDM terpolymer hasabout 5 to about 50 meq. sulfonate groups per 100 grams of sulfonatedpolymer, more preferably about 5 to about 40; and most preferably about7 to about 20. The meq. of sulfonate groups per 100 grams of polymer isdetermined by both titration of the polymeric sulfonic acid and DietertSulfur analysis. In the titration of the sulfonated polymer, the polymeris dissolved in solvent consisting of 95 parts of toluene and 5 parts ofmethanol at a concentration level of 50 grams per liter of solvent. Thesulfonated EPDM terpolymer is titrated with ethanolic sodium hydroxideto an Alizarin-Thymolphthalein end-point.

The sulfonated EPDM terpolymer is gel free and hydrolytically stable.Gel is measured by stirring a given weight of polymer in a solventcomprised of 95 toluene-5-methanol at a concentration of 5 wt. %, for 24hours, allowing the mixture to settle, withdrawing a weighed sample ofthe supernatant solution and evaporating to dryness. Hydrolyticallystable means that the acid function, in this case the unneutralizedsulfonate groups, will not be eliminated under neutral or slightly basicconditions to a neutral moiety which is incapable of being converted tohighly ionic functionality.

Neutralization of the sulfonated EPDM terpolymer is done by the additionof a solution of a basic salt to the unneutralized sulfonated EPDMterpolymer dissolved in the mixture of the aliphatic alcohol andnon-reactive solvent. The basic salt is dissolved in a binary solventsystem consisting of water and/or an aliphatic alcohol. The counterionof the basic salt is selected form a carboxylic acid having from about 1to about 4 carbon atoms, a hydroxide, or alkoxide having about 1 toabout 4 carbon atoms, and mixtures thereof. The preferred neutralizingagent is a metal acetate, more preferably zinc acetate. Sufficient metalsalt of the carboxylic acid is added to the solution of the acid form ofthe elastomeric polymer to effect neutralization. It is preferable toneutralize at least 95% of the unneutralized sulfonate groups, morepreferably about 98%, most preferably 100%. Examines of metal oxidesuseful in preparing metal sulfonates are MgO, CaO, BaO, ZnO, Ag₂ O, PbO₂and Pb₃ O₄. Useful examples of metal hydroxides are NaOh, KOH, LiOH,Mg(OH)₂ and Ba(OH)₂. Alternatively, the unneutralized sulfonated EPDMterpolymer can be neutralized with an organic amine such as described inU.S. Pat. No. 3,642,728 which is incorporated herein by reference.

B. Plasticizers

The metal sulfonate containing polymers at higher sulfonate levels canpossess extremely high melt viscosities and are thereby difficult toprocess. The optional addition of ionic group (preferential)plasticizers markedly reduces melt viscosity and frequently enhancesphysical properties. To the neutralized sulfonated EPDM terpolymer isadded, in either solution or to the crumb of the sulfonated EPDMterpolymer, a preferential plasticizer selected from the groupconsisting of carboxylic acids having about 5 to about 30 carbon atoms,more preferably about 8 to about 22 carbon atoms, or basic salts ofthese carboxylic acids, wherein the metal ion of the basic salt isselected from the group consisting of aluminum, ammonium, lead andGroups IA, IIA, IB and IIB of the Periodic Table of Elements andmixtures thereof. The carboxylic acids are selected from the groupconsisting of lauric, myristic, palmitic or stearic acids and mixturesthereof; e.g., zinc stearate, magnesium stearate, or zinc laurate.

The preferential plasticizer is incorporated into the neutralizedsulfonated EPDM terpolymer at about 1 to about 50 parts by weight basedon 100 parts by weight of the neutralized sulfonated polymer, morepreferably at about 2 to about 25, and most preferably at about 3 toabout 20. The metallic salt of the carboxylic acid can also be used asneutralizing agent. In the case of the neutralizing agent andplasticizer being the identical chemical species, additional metallicsalt is added over the required levels of neutralization. Alternatively,other preferential plasticizers are selected from amines, amides such asstearamide, ammonium and amine salts of carboxylic acids and mixturesthereof. The preferred plasticizers are selected from carboxylic acidshaving about 8 to about 22 carbon atoms or metallic salts of thesecarboxylic acids and mixtures thereof. The resultant neutralizedsulfonated elastomeric polymer with preferential plasticizer is isolatedfrom the solution by conventional steam stripping and filtration.

C. Commercial Tackifier Resins

To the hot melt adhesive composition is added a commercial tackifyingresin having a softening point of about 0° to about 160° C., morepreferably about 50° to about 140° C. and most preferably about 70° to120° C. A variety of commercial tackifier resins are available. Some ofthese resins contain α and/or β pirene base polyterpene resins as themain ingredient while others are derived from the polymerization ofpetroleum or coal distillates which consist of aliphatic dienes, monoand di-olefins and cyclic olefins having about 5 to about 6 carbonatoms. The latter type of tackifiers have primarily piperlene and/orisoprene structure. A general but excellent description of tackifyingresins derived from Petroleum derivatives can be found in, for example,Encyclopedia of Polymer Science and Technology, Vol. 9, Pages 853 to860, chapter by John Findlay, Published by John Wiley & Sons, NY (1968).

Typical but non-limiting tradenames of these commercial tackifiers areWingtak of Goodyear, Escorez of Exxon, Piccolyte of Hercules and Zonrezof Arizona Chemicals. Recently these and various other companies havealso started marketing relatively higher softening point resins. Theseare generally modified aliphatic hydrocarbon resins and/or hydrogenatedpolycyclics. The physical appearance of these commercial tackifyingresins varies, depending upon their softening point, they can be eitherviscous liquids or light-colored solids at room temperature. Most oftentheir initial color (Gardner) is about 3.0 to about 7.0 and the densityfrom about 0.7 to 1.0 gm/cm³ at room temperature. The acid number ofthese resins is usually less than 1. In general, the molecular weight ofthese commercial tackifying resins is not homogeneous, it spreads thenumber average molecular weight Mn can be from about 300 to about 5000and more preferably about 500 to about 2000 and most preferably about700 to 1600.

As well-known to those familiar with the use of tackifying resins,because of their wide range compatability, any of them can be used withsulfonated polymers in proper formulation, which will yield adhesivesystems of varying physical characteristics. To cite an example in thepresent invention, the tackifying resins used are those based onhydrocarbon resins.

These hydrocarbon tackifier resins are incorporated into the hot meltadhesive composition at about 25 to about 250 parts by weight per 100parts by weight of the highly unsaturated hydrocarbon rubbers, morepreferably about 30 to about 125 and most preferably about 35 to about100.

D. Method of Forming Blend Adhesive Composition

The blend compositions of the neutralized sulfonated elastomeric polymerwith or without preferential plasticizer and the hydrocarbon tackifierresin can be formed by techniques well known in the art. For example,the blend composition of the hot melt adhesive can be compounded on ahot two-roll mill. Other methods known in the art which are suitable formaking these compositions include those methods employed in the plasticand elastomer industries for mixing polymer systems. An excellentpolymer blend composition of this invention can be obtained through theuse of a high shear batch intensive mixer called the Banbury.Alternatively, economic advantages in terms of time and labor savingscan be obtained through the use of a Farrell Continuous Mixer, a twinscrew extruder, or tandem extrusion techniques which are continuousmixing types of equipment. The Banbury mixing device is the preferredbatch type mixer, and the twin screw extruder is the preferredcontinuous mixer.

E. Extended Blend Adhesive Composition

To the blend compositions of the hot melt adhesive compositions can beadded fillers which are selected from the group consisting of talcs,ground calcium carbonate, water precipitated calcium carbonate,delaminated, calcined or hydrated clays, silicas, and carbon blacks, andmixtures thereof. These fillers are incorporated into the blendcomposition at about 1 to about 150 parts by weight per 100 parts byweight of the neutralized sulfonated elastomeric polymer, morepreferably at about 20 to about 150; and most preferably at about 30 toabout 100. Typically, these fillers have a particle size of about 0.03to about 20 microns, more preferably about 0.3 to about 10, and mostpreferably about 0.5 to about 10. The oil absorption as measured bygrams of oils absorbed by 100 grams of filler is about 10 to about 100,more preferably about 10 to about 85 and most preferably about 10 toabout 75. Typical fillers employed in this invention are illustrated inTable I.

F. Oil Extended Adhesive Compositions

It is observed that the blend composition of the instant invention canalso include oils to further improve low temperature properties and tackcharacteristics of the resulting adhesive levels of oil of less thanabout 25 parts by weight per 100 parts of the neutralized sulfonatedelastomeric polymer rubber can be incorporated, more preferably about 1to about 20 parts. Oils are particularly useful when high levels ofpetroleum resin tackifiers are used since such materials can harden theresulting composition. Oils can further soften and reduce the cost.Typical oils that can be used may be low viscosity aromatic, naphthenicor paraffinic petroleum oils, having less than 2 weight percent polartype compounds. Typical oils are illustrated in Table II.

                                      TABLE I                                     __________________________________________________________________________                          Oil           Avg.                                                            Absorption grams                                                                            Particle                                                        of oil/100                                                                             Specific                                                                           Size                                      Filler        Code #  grams of filler                                                                        Gravity                                                                            Micron                                                                             pH                                   __________________________________________________________________________    Calcium Carbonate Ground                                                                    Atomite 15       2.71      9.3                                  Calcium Carbonate Pre-                                                                      Purecal U                                                                             35       2.65 .03-.04                                                                            9.3                                  cipitated                                                                     Delaminated Clay                                                                            Polyfil DL                                                                            30       2.61 4.5  6.5-7.5                              Hydrated Clay Suprex           2.6  2    4.0                                  Calcined Clay Icecap K                                                                              50-55    2.63 1    5.0-6.0                              Magnesium Silicate                                                                          Mistron Vapor                                                                         60-70    2.75 2    9.0-7.5                              __________________________________________________________________________

                  TABLE II                                                        ______________________________________                                                           Vis-               %     %                                                    cosity       %     Aro-  Satur-                            Type Oil                                                                              Oil Code # ssu     M.sub.n                                                                            Polars                                                                              matic rates                             ______________________________________                                        Paraffinic                                                                            Sunpar 115 155     400  0.3   12.7  87.0                              Paraffinic                                                                            Sunpar 180 750     570  0.7   17.0  82.3                              Paraffinic                                                                            Sunpar 2280                                                                              2907    720  1.5   22.0  76.5                              Aromatic                                                                              Flexon 340 120     --   1.3   70.3  28.4                              Naphthenic                                                                            Flexon 765 505     --   0.9   20.8  78.3                              ______________________________________                                    

G. Method of Fabrication of Adhesive Compositions

Because of the significant advances in the packaging technology, the hotmelt adhesive compositions can be used by conventional polymerfabricating techniques. After the blending is complete, the adhesivemass can either be extruded and/or calendered to a uniform thickness ontop of the substrate which would be paper, cloth, aluminum foil or glassfabric. The temperature and the through put of the extrusion arevariable depending upon the viscosity of the tackifying mass and thedesired coating thickness. Typically the temperature of extrusions androlls may be from about 200° to 400° F. The substrates on backings towhich the pressure sensitive adhesive compositions are applied may be ofvarious porous or nonporous types and they may be organic or inorganicin nature. Most generally, these materials are those which arecustomarily employed in pressure sensitive tapes, either the cloth orpaper backed types or tape backings made of synthetic materials, forexample, polyesters such as the copolymer of ethylene glycol withterphthalic acid, vinyls such as a copolymer of vinylidene chloride andvinyl chloride, or a copolymer of vinylidene chloride withacrylonitrile, cellophane, cellulose acetate, polyvinyl chloride,polyvinyl acetate, polypropylene, polyethylene, ethylene-propyleneplastic copolymer. Sheetings and tapes of cloth or textiles of eithernatural or synthetic fiber origin, such as glass fiber cloth, wood, andfinally sheets or strips of metals such as steel, copper, aluminum, andalloys thereof can also be employed. In general, the backing employedare those which have been heretofore been conventionally employed inpreparing pressure sensitive labels, tapes, sheetings and the like andthe selection of any particular substrate material is not a specificnovel feature of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The advantages of the hot melt adhesive compositions of the presentinvention can be more readily appreciated by reference to the followingexamples and tables. Unless otherwise specified, all measurements are inparts per hundred by weight.

EXAMPLE I

Five hundred grams of an EPDM terpolymer (MD-76-5) was dissolved underagitation in 5000 ml. of n-hexane at about 40° C. After all this polymerwas dissolved, the solution was cooled to low temperature and 17.22 ml.of active anhydride (182.25 mmoles) was added. After that, whilestirring the mixture 6.31 cc of 95% H₂ SO₄ (11.50 m-moles) was addeddropwise, the stirring of the solution was continued for an additional30 minutes for the sulfonation reaction to complete. After this period,the sulfonation reaction was inactivated by adding 28.63 gm of zincacetate dissolved in 400/20 ml. mixture of CH₃ OH/H₂ O. Antioxidant 2246(2.5 gm) was then added to the cement and stirring was continued for anadditional 30 minutes. The resultant neutralized sulfonated EPDMterpolymer was isolated by steam stripping. It was then washed withdistilled water and pulverized with water in a Waring Blender, followedby filtering by a rubber drum. The final drying of the polymer was donein an aromatic dryer at 100° C.

The sample is identified as neutralized sulfonated EPDM terpolymer 1-2.

The preparation technique of a sulfonated EPDM terpolymer Zn salt having10 meq. sulfonate groups (Samples 1-1) were the same as above of sample1-2. The only difference was in the amount of various chemicalingredients required for the sulfonation and neutralization reaction.The approximate amount of acetic anhydride used (for sample 1-1) was8.90 ml (94.50 mmoles), 3.30 H₂ SO₄ 3.30 cc (58.30 m-moles) and zincacetate 15.40 gms.

The sulfur analyses on samples 1-1 and 1-2 was done by Dietert Sulfuranalysis and these polymers were found to have sulfonate group of 20meq. and 10 meq. per 100 gm of sulfonated polymer.

EXAMPLE 2

The neutralized sulfonated EPDM terpolymers of Example I (1-1 and 1-2),and other similarly prepared samples both with higher and lowersulfonation levels and a tackifier resin such as Wingtak Plus or Escorez1310 were dry blended in the proportion as indicated in Table III andsubsequently mixed into a homogenous blend on a hot two-roll mill atabout 150° C. for about 15 minutes. Blends 3-2 and 3-3 incorporate ionicpreferential plasticizer stearic acid. Blend 3-4 is one of the formulafor hot melt adhesive compositions based on commercial components havingexcellent properties and is included here for comparative purposes.

CONCLUSIONS

Table IV illustrates various qualitative and quantitative properties ofthese blends. It can be readily noted that the blends incorporating thesulfonated polymers, Blends 3-1 and 3-2, are not only very tacky buthave relatively good green strength. The strength of such materials canbe controlled by the proper changes in the formulations and/or by addingthe preferential plasticizers and processing oils. Such systems areexcellent for various pressure sensitive adhesive applications,especially as hot melt adhesives. Because of their high green strength,these materials will undergo very little creep deformations and thustheir shelf use life can be expected to be significantly better overthose conventional adhesives. In accordance with their high strength,their high temperature properties will also be improved. And thus forexample, laminates prepared using such adhesives will not be expected todistort due to flow or failure if subjected to sudden temperature orpressure changes.

Quantitative numbers on the peel strength of these blends are listed inthe fifth column of Table IV.

                  TABLE III                                                       ______________________________________                                        COMPOSITIONS OF BLENDS OF SULFONATED                                          POLYMERS WITH PETROLEUM RESINS                                                Blend #          3-1     3-2     3-3   3-4*                                   ______________________________________                                        Sulfo EPDM Zn Salt                                                            (˜10 meq.) 50      --      --    --                                     Sulfo EPDM Zn Salt                                                            (˜20 meq.) --      50      --    --                                     Sulfo EPDM Zn Salt                                                            ( 30 meq.)       --      --      50    --                                     Kraton-1107*     --      --      --    50                                     Wingtak Plus     --      --      --    50                                     Escorez-1310     50      50      50    --                                     Stearic Acid     --       4       4    --                                     ______________________________________                                         *This blend is included here for comparative purposes. Kraton 1107 is         block copolymer of the structure ABA in which A is a block of styrene         (styrene content about 15% by weight) whose number average molecular          weight is in the range of 10,000 to 30,000. B is an elastic block of          isoprene (isoprene content about 85%) having a number average molecular       weight of 100,000.                                                       

                  TABLE IV                                                        ______________________________________                                        QUALITATIVE AND QUANTITATIVE PROPERTIES                                       OF VARIOUS BLENDS OF SULFONATED POLYMERS                                      WITH PETROLEUM RESINS                                                                                              Peel*                                                                         Strength                                        Green                         (Pound-                                  Blend #                                                                              Strength   Tackiness   Clarity                                                                              Force)                                   ______________________________________                                        3-1    High       Very Tacky  Clear  9.4                                      3-2    High       Slightly    Light  1.23                                                       Tacky       Tan                                             3-3    Very High  Slightly    Light  0.78                                                       Tacky       Tan                                             3-4    High       Tacky       Clear  11.9                                     ______________________________________                                         *Average value of minimum three measurements                             

                  TABLE V                                                         ______________________________________                                        FLOW OR CREEP CHARACTERISTICS OF THE BLENDS                                   OF SULFONATED EPDM'S WITH PETROLEUM RESINS                                    Thickness of sample (in inches) at                                                                    % Change in                                           Time                    height                                                Blend #                                                                              0-hr.  1-hr.   2-hrs.                                                                             3-hrs.                                                                             19-hrs.                                                                             in 19 hrs.                              ______________________________________                                        (Sample size - Diameter = 0.250  Load = 1000 gms)                             3-1    0.124  0.076   0.068                                                                              0.064                                                                              0.047 -62%                                    3-2    0.131  0.118   0.113                                                                              0.113                                                                              0.107 -18%                                    3-3    0.132  0.113   0.110                                                                              0.110                                                                              0.109 -17%                                    3-4    0.114  0.0650  0.063                                                                              0.057                                                                              0.050 -56%                                    (Sample size - Diameter = 0.37"; load = 1000 gms)                             3-1    0.126  0.104   0.101                                                                              0.101                                                                              0.091 -28%                                    3-2    0.128  0.124   0.122                                                                              0.121                                                                              0.121  -5%                                    3-3    0.125  0.119   0.119                                                                              0.119                                                                              0.114  -9%                                    3-4    0.131  0.100   0.099                                                                              0.092                                                                              0.084 -36%                                    ______________________________________                                    

The peel strength values were obtained by a method similar to ASTM D-429adhesion test. In brief, the samples were sandwiched between Mylarsheets and pressed to a thickness of about 25 mils using a hot press.Rectangular strips of 1/2" width and 3" long were cut and 90° peel testswere performed on an Instron at room temperature. The resin freesections of the Mylar film were clamped into air jaws to avoid anyslippage during pulling. The samples were pulled at 5"/min. crossheadspeed. The force and elongation of the samples were recorded on a striprecorder. The force necessary to separate the Mylar sheets was taken asthe peel strength of the blend. Various runs were made and the averageof the initial peak values were recorded and are reported in the fifthcolumn of Table IV.

DISCUSSIONS

The flow behavior or more specifically the creep resistancecharacteristics of the adhesive blends is a critical property. In orderto assess the creep behavior of our adhesive blends, an experiment verysimilar to that of the ASTM D-395, l which is a standard test fordetermining the compression set behavior of elastomers and plastics, wasdesigned. Various sample pads of appropriate thickness were prepared byhot compression molding techniques in between the Mylar sheets. The discshaped samples were punched out from these pads and were placed undervarious desired loadings. Before the application of load the initialthickness of the samples were recorded and the samples rested on a flatsurface. The size of the various samples and loadings are listed inTable V. Frequently, at convenient time intervals the loads from thesamples were removed and the height (or the thickness) of the sampleswere measured. Thickness data as a function of time appear in thevarious columns of Table V. The samples which decreased in heightobviously had undergone flow and thus should have relatively poor creepcharacteristics. Noting the various numbers of Table V, it is observedthat the Blend #3 -1, which is a blend of the sulfonated EPDM of lowestsulfonate content terpolymer with the resin showing poor creepresistance as opposed to the blends which contain higher levelsulfonated EPDM polymers. Broadly speaking, this is consistent with ourexperience with the use of sulfonated polymers in their bulk state, ingeneral. As more and more ionic linkages are introduced the strength ofthe sulfonated polymers increase and their creep properties improve. Inthe adhesive blend systems this behavior is observed with respect tocreep (see Blend #3-2 and 3-3) albeit with loss in their tackcharacteristics, as observed from Table IV. The tack characteristics,however, in some cases can readily be modified or improved by properchoice of resins, the amount of oil, plasticizers etc.

Two different sets of experiments employing different size samples wereused for determining the creep characteristics of the adhesive blends.Both sets of the data are reported in Table V. Blend number 3-4 in TableV is based on a block copolymer and hydrocarbon resin and is shown onlyfor comparison. This blend was compression molded and the resultant padwas not uniform in thickness; therefore the specific thickness valuesare subject to more error than is the case for the other blends. In anyevent it is apparent that this sample does possess rather poor creepresistance, but relatively good peel strength values.

What is claimed is:
 1. A hot melt adhesive composition whichcomprises:(a) a neutralized sulfonated EPDM terpolymer having about 5 toabout 50 meq. of neutralized sulfonated groups per 100 grams of saidneutralized sulfonated EPDM terpolymer; and (b) about 25 to about 250parts by weight of a hydrocarbon resin of a petroleum or coal tardistillate per 100 parts by weight of said neutralized sulfonated EPDMterpolymer.
 2. A hot melt adhesive composition according to claim 1,wherein said EPDM terpolymer consists of about 40 to about 65 weightpercent of ethylene, of about 25 to about 53 weight percent of propyleneand of about 2 to about 10 weight percent of a non-conjugated diene. 3.A hot melt adhesive composition according to claim 2, wherein saidnon-conjugated diene is 5-ethylidene-2-norbornene.
 4. A hot meltadhesive composition according to claim 1, wherein said neutralizedsulfonate groups are neutralized with a counterion selected from thegroup consisting of ammonium, aluminum, antimony, iron, lead and GroupsIA, IIA, IB and IIB of the Periodic Table of Elements.
 5. A hot meltadhesive composition according to claim 1, wherein said neutralizedsulfonate groups are neutralized with zinc ions.
 6. A hot melt adhesiveaccording to claim 1 further including about 1 to about 50 parts byweight of an ionic preferential plasticizer per 100 parts by weight ofsaid neutralized sulfonated EPDM terpolymer, wherein said preferentialplasticizer is selected from the group consisting of carboxylic acidshaving about 8 to about 22 carbon atoms, metallic salts of saidcarboxylic acids, amides having an aliphatic group of about 8 to about22 carbon atoms, amines, ureas and thioureas and mixtures thereof.
 7. Ahot melt adhesive composition according to claim 6, wherein saidsulfonated neutralized EPDM terpolymer contains about 7 to about 20 meq.of neutralized sulfonated groups per 100 grams of polymer.
 8. A hot meltadhesive according to claim 7, wherein said preferential plasticizer issaid metallic salt of said carboxylic acid.
 9. A hot melt adhesivecomposition according to claim 8, wherein said metallic salt of saidcarboxylic acid is zinc stearate.
 10. A hot melt adhesive compositionaccording to claim 1 or 6 further including about 1 to about 150 partsby weight of a filler per 100 parts by weight of said neutralizedsulfonated EPDM terpolymer, said filler being selected from the groupconsisting of calcium carbonates, silicas, carbon blacks, clays andtalcs and mixtures thereof and/or less than about 100 parts by weight ofan oil having less than 2 weight percent polars per 100 parts by weightof said neutralized sulfonated EPDM terpolymer.
 11. A hot melt adhesivecomposition according to claim 1 or 8 wherein said hydrocarbon resin hasabout 5 to 6 carbon atoms and consists of aliphatic dienes, mono anddiolefins and cyclic olefins.